The present invention relates to a mechanical brake actuating device for spot-type disc brakes comprising a brake caliper embracing the brake disc inwardly or outwardly, at least one leg of the brake caliper having a cavity, preferably an axial, cylindrical bore, an actuating spindle axially disposed in the cavity, and cooperating with an actuating nut disposed in the cavity in such a manner that a brake shoe applying member is advanced in the event of an axial relative displacement between the spindle and the nut caused by means of a relative rotation between the actuating spindle and the actuating nut due to an actuating means, and an automatic adjusting device for the brake shoe applying member disposed in the cavity.
In a known spot-type disc brake adapted to be actuated both hydraulically and mechanically, for instance German Patent DE-AS No. 1,575,996, a brake piston is located axially freely movable on the actuating nut and for being actuated is acted upon from the inside by an adjusting spindle cooperating with the adjusting device. In this known spot-type disc brake, it is required for the resetting of the adjusting device, after a brake pad replacement, to unscrew a screw cap and to take out a wedge. This method not only involves intricate work, but also bears the risk of losing the unscrewed parts. Besides, the wedge may be jammed by corrosion, so that it cannot be removed without difficulties during pad replacement.